In recent years, IP broadcasting systems which, for example, form video contents into IP packets and distribute (or stream) them to a large number of unspecified viewers have been established. This type of systems uses IP network to distribute digital contents by terrestrial digital broadcasting or satellite digital broadcasting. Digital contents may be provided by a content provider.
New mobile broadband channels such as long term evolution (LTE) or worldwide interoperability for microwave access (WiMAX) have also been established. Along with development of the communication technology, an environment for providing services of a new style is in place.
Furthermore, systems in which users share video contents via video sharing sites have been established. This type of systems enables to open, in the Internet, video contents uploaded to a server by submitters.
In this technical field, it is important to stabilize, for each session, the sending rate of Transport Stream (TS) signals containing video data with high precision.
A Video on Demand (VOD) server distributes contents in response to a request from a viewer but the bit rate for each content is not always the same. To smoothly play back the contents on the reception side, it is necessary to distribute packets while keeping a stable sending rate for each session, as described above. If the total value of the sending rates in respectively sessions is small enough with respect to the bandwidth capacity (network bandwidth) of an interface involved in distribution of the packets, it is easy to stabilize the sending rate.
If, however, the total value of the sending rates comes close to the bandwidth capacity due to an increase in number of simultaneously formed sessions, the transmission timings for packets of the contents collide. Since a conventional technique transmits packets in the generation order, that is, in a first-come first-served manner, a packet which is postponed transmitting is delayed. Consequently, an interval at which packets reach the reception side becomes unstable, which results in deterioration of the quality of contents playback. Therefore, some measures for this problem are needed.